Electrical condenser and its manufacture



Sept. 22, 1936. P. E. EDELMAN ELECTRICAL CONDENSER AND ITS MANUFACTURE 7 Sheets-Sheet 1 Filed Aug. 30, 1929 Sept. 22, 1936. P. E. EDELMAN ELECTRICAL CONDENSER AND ITS MANUFACTURE Filed Aug. 30, 1929' 7 Sheets-Sheet 2 lzuzye22if f l @2299 E, ,Zjdeifizaw. 9 am Sept. 22, 1936.

Filed Au 50, 1929 v 7 Sheets-Sheet 3 f1. E6262 32am Sept. 22, 1936. p M N 2,055,216

ELECTRICAL CONDENSER AND ITS MANUFACTURE Filed Aug. 50, 1929 7 Sheets-Sheet 4 Jaye/ 2267 12/22/2905 gdaZflz/azzh Sept. 22, 1936. P. E. EDELMAN ELECTRICAL CONDENSER AND ITS MANUFACTURE Filed Aug. 30, 1929 7 Sheets-Sheet 5 Hliyp if M L Sept. 22, 1936. P. E. EDELMAN ELECTRICAL CONDENSER AND ITS MANUFACTURE Filed Aug. 30, 1929 7 Sheets-Sheet 6 W I Q 9flZQ 7206/6 0/ k/ziglp Z. Zzjdadvzam.

Sept. 22, 1936. p E, EDELMAN 2,055,216

ELECTRICAL CONDENSER AND ITS MANUFACTURE Filed Aug. 30, 1929 7 Sheets-Sheet 7 ;:12 106' I f L 11g j 45- Patented Sept. 22, 1936 UNITED STATES ELECTRICAL CONDENSER AND ITS MANUFACTURE Philip E. Edelman, Chicago, 111., assignor, by mesne assignments, to Robert T. Mack, trustee,

Chicago, Ill.

Application August 30,

14 Claims.

This invention relates to electrical condensers and their manufacture, and more particularly to electro-chemically prepared, hermetically sealed high voltage type condensers.

Heretofore, there has been difficulty in standardizing and producing uniform condensers able to withstand high operating voltages on continuous service. Paper condensers have been found both expensive and unable to withstand operating surge currents which commonly occur in circuits capable of alternating current resonance conditions. Wet electrolytic condensers have the fault of watering troubles, occurrence of short circuiting precipitates during use, loss of film on standing idle, and non-uniformity, as well as the undesirable large bulk of electrolyte required therefor. An object of this invention is to provide a high grade inexpensive high voltage type condenser which can be uniformly produced in quantity. A further object is to provide a condenser of self healing type when subjected to abnormal surge voltages. A further object is to provide a hermetically sealed condenser having the characteristics of long operating life, immunity to decay on standing idle during shipment or non-use, absence of watering troubles, ability to withstand extremes of temperature in shipment and in service, and small bulk and weight.

These and other objects, as will presently appear, are accomplished by this invention which is fully described in the'following specification and shown in the accompanying drawings, in which-#- Figure 1 is a plan view of a blank positive filming metal electrode prepared according to my invention;

Fig. 2 is a plan view of a partly developed form of the blank of Fig. 1;

Fig. 3 is a plan view of a filmed electrode prepared from a blank as shown in Fig. 2;

Fig. 4 is a perspective view of a processing rack showing the operating position of an electrode blank such as shown in Fig; 2, in which the processing electrolyte container is shown in dotted lines because the rack shown in Fig. 4 is also used for a drying rack in the manufacture of the processed electrode plates such as shown in Fig. 3;

Fig. 5 is a partly sectioned vertical elevation view showing a suitable means for impregnating with the operating electrolyte mass used in the completed condenser according to my invention;

Fig. 6 is a plan view showing one processed electrode plate covered by an impregnated fabric according to my invention;

Fig. 7 is a sectioned diagram of the essential relation of the parts of 6;

Fig. 8 is a schematic diagram showing the preferred structure according to Fig. 6

Fig. 9 is a diagram showing the assembly of a 1929, Serial No. 389,338

covered electrode plate as shown in Fig. 6 combined with a co-operating negative electrode;

Fig. 10 is a schematic diagram explanatory of the assembly according to Fig. 9;

Fig. 11 is a perspective view of 'a completed condenser roll containing two processed electrode plates and one co-operating negative metal strip prepared as aforesaid and shown in the preceding figures;

Fig. 12 is a front elevation of a part of an electrode terminal showing the manner of attaching a terminal wire thereto;

Fig. 13 is a view similar to that of Fig. 12 with the addition of the protective coating 5! applied to the finished terminal connection;

Fig. 14 is a perspective view showing the manner of applying the absorbent wrapper 53 applied to the processed condenser winding of Fig. 11;

Fig. 15 is a plan view showing the completed assembly according to Fig. 14;

Fig. 16 is a perspective view showing the condenser wrapped ready for assembly in a container;

Fig. 17 is a view similar to Fig. 16 in the case where two condenser rolls are assembled in series connection;

Fig. 18 is a diagrammatic representation of the essential relation of the electrodes and spacer elements used according to my invention;

Fig. 19 is a circuit diagram of a completed condenser block wired according to my invention;

Fig. 20 is a perspective view of a partly assembled condenser unit, according to Fig. 19, placed in a protective container;

Fig. 21 is a perspective view of the finished assembly in the container according to Fig, 20;

Fig. 22 is a diagram of a suitable means for preparing the mixture used for impregnating the spacer strips according to Fig. 5;

Fig. 23 is a diagram of the processing arrangement used to coat a di-electric layer of permanent characteristics on the processed electrodes prepared from blank sheet metal according to Fig. 1;

Fig. 24 is a diagram of the preferred form of ageing means employed according to my invention to place the assembled condenser rolls in operative condition;

Fig. 25 is a circuit diagram of an arrangement for testing completed condensers according to my invention;

Fig. 26 is a diagram .showing a use of my condenser;

Fig. 27 is a circuit equivalent to that of Fig. 26 shown in conventional manner for comparison to the diagram of Fig. 26;

Fig. 28 is a diagram of a suitable c cuit assembly or condenser rolls prepared as store said;

Fig. 29 is a diagram showing a further series connection for such condenser windings to operate on higher voltages; and

Fig. is a diagram of parallel connected condenser windings, such as shown in Fig. 25.

Owing to the elaborate nature of my invention in the mode of manufacturing the product, a single drawing would not adequately illustrate same, and I am showing same, step by step, in a series of co-operating and related drawings to make the invention clear to anyone skilled in this art. I am illustrating a preferred structure as an exemplification of my invention which has been proven to accomplish the objects stated- (I) Raw filming metal For raw material useful in preparing thesheet metal blank according to Fig. 1 I may use any suitable filming metal, such as aluminum or an alloy thereof, or tantalum, but I prefer to employ first grade soft aluminum of commerce rolled into'sheet form of thickness of the order of .006", free from -oil or grease. ,The width of the sheet aluminum may be selected at any convenient value, such for example. as 3 inches and the length of the blank I shown in Fig. 1 may similarly be predetermined according to the capacity desired in the finished icondenser product. I prefer to arbitrarily establish a desired capacity per unit plate blank, such as shown in Fig. 1 at-some value, such for example as mfd. per square inch area thereof, and to appropriately proportion the processing of said blank to attain and control such selected value as selected within close limits. This is more convenient than any attempt to govern fractional dimensions of the blank I of Fig. 1 to attain desired capacity vvalue thereof in the finished confilming metal aforesaid, 'I

denser, and lends uniformity to the processing, in, that the treating voltage used, can be readily proportioned to .attain the desired capacity value in a given area of the blank I.

Referring now, more particularly to Fig. 1, the has rounded or smoothed corners cutat 2, 2, 2, 2; also a slit 3 and a slit 4 sheared therein to form connector pieces 5, .4, respectively continuous with the electrode blank I. smooth. Fig. 2 shows how connector strip portion is bent over and folded fiat at I to form a right angled extension piece ,4 from connector portion 5 As shown in Fig. 3. the strip portion, 4, of Fig. 2, is finally cut off at the position shown by line 8' for reference purposes only, leaving connector portion 5 folded up from the processed electrode I at fold II). A colored line 9 is applied to tab terminal 5 with some insulating pigment, such as colored lacquer to indicate the capacity value of the processed plate I of- Fig. 3. The subscript a used in Fig. 3 to designate the processed plate I indicates for reference pur-' poses only, that said electrode plate has been coated with a permanized di-electric coating argcording to the herein described processing.

(II) Processing of blanlc electrodes The processing of blanks prepared according to Fig. 2 is conveniently carried out by means of a rack II shown in Fig. 4. Rack II has a plurality of connector clips I2, by means of which blanks I. of which one example is shown in operative position in the figureyare secured in alignment with respect to processing negative electrode I9, and also by means of which blanks,

This blank I is to be kept clean and tainer 20. shown by dotted lines, for explanatory purposes only, and dried, without necessitating handling of the treated blanks I by an .operators hands. Processing electrode I9 is preferably a round inch diameter Duriron rod, about 12 inches long, and secured by a collar II to a Bakelite support strip I5. A terminal I8 is provided on collar II. The Duriron rod I9 is thereby adapted to be removed from the Bakelite support I5 while rack II is used for drying one batch of processed plates, such as I. A plurality of similar racks II, as shown in Fig. 4, is required for continuous manufacture of the said condenser plate I. The Bakelite Support I5 has indented portions I6, I6 formed thereon to mitigate current leakage caused by condensation of conducting vapor on strip I5 during operation of ,rack II in the processing as hereinafter set forth. Strip I5 is supported suitably from rack II so that rod I9 hangs substantially centrally with respect to connector clips I2, I2 etc. Back I I is preferably made from tinned brass and has an extension rim I4 adapted to fit over treating container 20 at the top thereof. A connector terminal I3 is provided on rack II. The treating solution used inFig. 4. is placed in the container 20 indicated by dotted lines to within V inch of the top thereof as indicated by dotted line 2I and maintained replenished to substantially this level. A suitable material for the container, shown by dotted lines, 20, is glazed stoneware. A characteristic blue deposit appears on the processed blank portion d, corresponding to the junction between liquid level '2I and the atmosphere. The clips I2, I2, I2 etc., must be spaced so that adjacent blanks I held thereby do not touch. each other and do not touch electrode'rod I9 and do not touch anypor I5 of Bakelite support I5, may be used to hang up r ck II during drying of plates, such as I after trea ment in container 20.

r (III) Impregnation of fibrous spacer sheets Impregnation of the spacerfabriczused according to my invention will next be described with reference to Fig. 5. In general, a gauze fabric I strip 39, about of an inch wider than the blank of Fig. 1, is uniformly impregnated;

with an operating chemical 24 to form an. electrode spacer material 39 Gauze 39 may be similar to best grade clean and close textured cheese cloth, such as is used for surgical dressings, cut to the aforesaid predetermined width and in lengths of about 350 feet or less. Any suitable equivalent material may be substituted for fabric 39, the essential characteristics being specified as,-uniform weave of textile or fibrous material characterized by a multiplicity of closely spaced pores in the strip 39. Gauze 39 is passed between guide rollers 40. The rollers .40 are journaled suitably" in a support dl carried by an impregnating container 23. A roller 43 is placed in operative position, as indicated in Fig. 5, in container 23, so that gauze 39 becomes impregnated with chemical mixture 24 as it is drawn therethrough. Squeeze or wrlnger rollers 35, 3'! journaled suitably in and supported by a support 3 carried by container 23, remove excess chemical 245 collected by gauze 39. A

drain return 35 returns the excess chemical 24 to container 23. A drum or reel 33 collects the impregnated gauze 39 as member 33 is rotated by means of crank 3| mechanically connected thereto in any suitable manner. Suitable supports 29, 29 are provided for placing drum 33 in operative position aligned with respect to rollers 35, 31, and drive shaft 32, actuated by means of crank 3|, is journaled suitably in member 29*. A base 30 supports member 29, heater 25, and container leg supports 28, 28. A Bunsen burner 25, or any equivalent source of heat, is used to heat the chemical mixture 24 in container 23. Thus, for example, a gas line 21 may feed burner 25 so that flame 25 warms container 23 to about 95 C., to maintain mixture 24 at a predetermined fiuidity during the impregnation of gauze 39. Container 23 must preferably be fabricated from cast aluminum to avoid contamination of the chemical mixture 24. The impregnated gauze 39" may be used as hereinafter set forth. It will be evident that a uniform coating and impregnation of gauze 39 is had in the manner set forth, whereby chemical mixture 24 impregnates the fibres of fabric 39, as well as fills the pore spaces therein. The treated gauze 39*? will have a light orange to tannish coloring caused bythe chemical mixture 24 employed according to this disclosure.

(IV) Covering plates with treated gauze The covering of processed plates with impregnated gauze will now be described with reference to Fig. 6. The processed and dried filmed electrode plate I is sandwiched in between the impregnated gauze 39 so that the latter overlaps plate I" and covers same, except at tab extension strip 5 thereof. Double layers of gauze 39 may be used to insure good coverage of plate A connector eyelet 44 may be attached to tab 5 at this time or later. The relation of plate I to gauze 39 is shown in Fig. '1. Fig. 8 shows this relation when double layers of gauze 39 are used. It may be here remarked that whereas chemical 24 is heated to obtain impregnation of gauze 39 as described for Fig. 5, the impregnated gauze 39 is preferably first cooled and applied to .cover plate when at room temperature. Chemical 24 is thus congealed in gauze 39 before same is used in the assembly, as in Fig. 6.

(V) The condenser winding The preparation of the condenser winding will now be described with reference to Fig. 9. In the case of polarized condensers for use on filter circuit service, the co-operating negative electrode for use with a positive electrode I covered by impregnated gauze 39 may be ordinary first grade soft aluminum sheet metal substantially .006" thick and either the same width as the width of plate i or else slightly wider. The sheet 45 may be of any other suitable metal besides aluminum. Metal 45 is smoothed between.

rollers 46 and started as a windingas end 45 thereof. An assembly 41, such as in Fig. 6, consisting of a positive plate coated with gauze covering 39 previously impregnated with chemical, as in Fig. 5, is inserted on sheet 45 as shown in Fig. 9 and the winding continued from end 45 so as to roll up element 41 interleaved with sheet 45. The winding of sheet 45 is continued after element 41 is rolled up so that metal' 45 extends beyond and over the element 41. second element like 41, or of different length may Then a' be wound up, and so on for any desired number of elements 41 to' be assembled in one roll. A completed roll 52, so made with two elements, such as 41 as diagrammed in Fig. 10, is shown in Fig. 11. The negative sheet 45 is overlapped around the roll 52 and has a tab terminal 49 brought up therefrom, while tab terminals 5 and 5 from two elements, such as 41, Fig. 10, are brought up in usual manner. A rubber band 48 holds the roll 52 in place for subsequent handling. The chemical in gauze 39 is held congealed therein at room temperature and does not run out.

While assembly numbered 52 in Fig. 11 is called a roll or condenser winding, it may be substantially fiat or any other desired shape according to the manner in which the end 45 of metal 45 in Fig. 9 is started for the winding.

The preferred manner of attaching a connector 4 (VI) Wrapping thev condenser As shown in Figs. 14 and 15, the assembly numbered 52, as in Fig. I is now wrapped with a layer of absorbent sheet fibrous material, such as blotter paper 53. Blotter paper 53 is held in place by a string or rubber band 54, Fig. 15. The function of blotter paper 53 is to protect roll assembly 52 when same is subjected to the thermic action of the sealing wax later used to fasten same .in a container as will presently appear, and further to absorb any excess chemical from impregnated gauzejfl which may appear at the rim margins of gauze 39 The next step, continuing the example described, is to wrap a varnished insulating paper 55 around assembly 52, as shown in Fig. 16, to substantially form a package wrapper 55 thereabout. Rubber bands or string 55 may be used to hold wrapper 55 in place. Terminals, 5, 5 and 49 are bent down over the top portion of wrapper paper 55, as shown in Fig. 16.

In the case of series assembly, a pair of condenser rolls' 52, 52 respectively will be assembled as in Fig. 17, placed so that a positive tab 5 of roll 5i. is adjacent to a negative tab connector 49 of roll 52. Then an eyelet 44 is driven through 5 and 49 to electrically join'roll condenser 52 in series with roll condenser 52*. The series connected rolls 52 and 52 may then be wrapped as in the example shown in Fig. 16.

A roll such as 52 may have one or more positive plates, such as l, and a suitable manner of assembling five such plates for example, is shown in Fig. 18. A plurality of separated prepared plates I, l etc., some of which may be of different lengths than others thereof, are placed between impregnated gauze strips 39 and adjacent to a co-operating common negative aluminum strip 45, so that the whole may be rolled up as an integral condenser winding in the aforesaid manner.

(VII) Circuit connection assemblies Circuit connections and assemblies suitable for use with my invention are shown only by way of example. Thus, in Fig. 19, a negative terminal filled with parafiin or other kind of wax and completed as shown in Fig. 21. Wires 53, 5t, 55, 58 may be appropriately colored to distinguish same according to the connections of Fig. 19, and are brought out from container 58 through a rubber grommet 59 attached to the cover of can 58.

15 (VIII) Preparation of the operating chemical The preparation of chemi al 24, used as aforesaid, is illustrated in Fig. 2 The mixture 24 is placed in an aluminum cooking vessel 60 supported by members 6|, 6|, so that a heater 62 can 0 warm mixture 25 in the vessel 80. Container 50 has a cover 64 arranged so that a thermometer 65 may be inserted into mixture 28. An air space 53 must be left above the level of mixture 28, as same expands considerably during the cooking 25 operation. Cover 68 has a stir shaft 61 joumaled therein at 59. A crank 58 operates shaft 61 .to which a small propeller element 66 is attached; in order that mixture 28 may be agitated and stirred during the cooking thereof. A vent hole 30 I8 is provided in cover 5.

The chemical mixture 26 consists preferably of pure powdered gum arabic dissolved in hot glycerine, in about the following proportions:

35 Pounds C. P. glycerine 40 XXX grade best powdered gum arabic, clear white 10 More or less gum arabic may also be used if de- 40 sired, but the stated proportion is found to be very suitable for the purpose.

The preferred manner of cooking the mixture 251s to first warm the glycerine content thereof to about 100 (2., whereupon the powdered gum arabic previously weighed out in correct amount is added and stirred in vesselfifl. As a precaution, a large air space 53 is allowed in vessel 60 because glycerine is inflammable at high tempera- I ture if permitted to spill over the top of vessel 60 50 to reach heater 52.

The cooking with occasional agitation continues for a period of about 30 minutes with the heat from heater 62 proportioned so that by the end of this time the thermometer 65 will show a reading between 140 C. and 150 C. The temperature should never be raised much higher than 140 0., as the mixture 26 begins to expand its volume rapidly at about such limiting temperature during the cooking thereof. The completed 60 batch of chemical 28 will now have alight tannish "to orange color and immediately after cooking will be in thin hot liquid form which should be poured through a cheese cloth filter into a storage container and kept closed from the atmosphere. 5 It congeals on cooling to a thick syrup or semigummy mass of relatively slight fluidity and must be ire-warmed to again bring said mass to fluidity, as set forth in the description. of Fig. 5, but never boiled or burned. For restoring fluidity for im- 70 pregnation purpose, it is only necessary to gently re-warm the chemical mixture 28 to about 90 C. to bring it into liquid state of sufiicient fluidity for such use. The mixture. 26 is entirely stable and can be used at any time after its preparation. 7 It does not attack aluminum. The aforesaid parallel connected racks II, Il II II".

mixture 24 affords an excellent high voltage op- (IX) Coating di-electric film on electrode plates The preferred manner of preparing the di-electric coating on plates I will now be set forth with reference to Fig. 23.

Ashunt generator l] with a no-load voltage of 750 volts has a field winding 12 and controlling resistance rheostat 13 connected to switches I4,

16. A voltmeter l5 and an ammeter ll indicate the current and voltage used. A clock I6 shows the time elapsed for the treatment processing. A plurality of treating containers, such as 20, 20 20, 20 are arranged with treating racks, I I, H H II, as in Fig. 4. Blank filming metal sheets, I, as in Fig. 2 are placed in position as'in Fig. 4,

a few such blanks I, I, being added to rack II at a time, in order not to overload generator 'II. Additional plates I, I, are added at intervals of a few minutes apart as the current passed by previously treated plates diminishes and permits new plates to be added as aforesaid.

Switches I9, 88, BI, 82, 83, 88, 85, and I8 control the circuit connections for series and later for parallel operation of the two respective treating rack groups II, II and Il II". This mode of operation is employed to fully utilize the output of generator H to best advantage, because in the processing of a plate I the initial current required is large, but rapidly diminishes to a small value in a few minutes of time, as shown by clock 16 and meters TI and 15.

To start with, two blank plates I may be placed in each treating container 20, 20 20 20, while the switches are manipulated so that racks II and H are in parallel, racks II and Il are in parallel, but the II, I I3 are in series with respect to the groups It, II. This is accomplished by opening switch 78, closing switch 19, closing switches 82, 83, 8G, 85 and 80, and opening switch 8i. This series connection will be used until, the racks such as l I are all filled with plates I, I etc., in process. Switches 16, 7 5 must be open while new plates, such as I are added to racks, such as II. The electrolyte used in containers such as 28 will presently be specifiedand is a clear solution so that plates I under'treatment can be observed by an operator. After racks I I, II, II II are filled with plates being treated, the operation is for the time being terminated at the end of ten minutes elapsed as shown by clock 16, whereupon the switches are now manipulated to obtain parallel connection as follows. Switch BI is closed, switch 18 is closed, and switch 79 is opened. The switches I 5 are then closed to apply the full voltage from generator II to the Rheostat i3 is appropriately regulated at thestart of both series and parallel treating operations so as not to overload generator I I, thereby causing the initial voltage used therefrom to be lower and gradually increased to the maximum as the resistance of rheostat I3 is reduced to its mini- 'mum position or value. Thus, for the first parallel operation, the voltage shown by meter I5 may start as low as 250 volts and be increased in a short time up to 750 volts; while for parallel operation, as aforesaid, the voltage may start at 325 volts and terminate at 480 volts, as controlled by rheostat I3. The parallel operation is arbitrarily predetermined at a fixed interval of time, such as 40 minutes. During the operations aforesaid, the treating electrolyte in jars 20, 20 20 20 will be occasionally replenished as required with diluted treatingsolution or distilled water as may be necessary to maintain correct liquid levels. As set forth in conjunction with Fig. 4, the characteristic blue linemarking 22 appears on plates I, being processed, and serves as a guide for the operation.

Upon completion of the p ocessing set forth,

racks II, II II II, are removed from containers 20, 20 20 20 and the processed plates, l, I, etc., held on racks aforesaid, are permitted to dry while held by said racks. Meanwhile duplicate racks may be placed in operating position on containers 20, 20 etc., and the operation repeated as aforesaid. The dried processed plates I are then finished as shown and set forth for Fig. 3, and suitably marked by identification marker 9. They may be stored or used as desired and do not deteriorate on standing or storage in a clean container or in clean air.

(X) The treating electrolyte The treating electrolyte preferred for use in containers 20, 20 etc., is a clear solution of distilled water containing both ammonium bitartrate and ammonium hepta-molybdate in about the following proportions:

Distilled water 5 gallons Ammonium bitartrate, C. P 1 to 1 ounces Ammonium hepta molybdate,

C. P. crystals to ounce For replenishing or make up solution to maintain liquid level in container 20-, for example, the above mixture may be diluted by adding ten parts of distilled water to one part of the aforesaid solution. In preparing the solution the ammonium bitartrate is to be separately dissolved in a portion of the aforesaid distilled water and the ammonium hepta-molybdate is to be dissolved in the remainder of said distilled water, then the two aforesaid solutions are to be mixed and agitated to form a single electrolyte solution. I prefer to pour this solution through a tinned iron funnel into a glass container, as the contact of said funnel is observed to influence the solution favorably and most probably by catalytic contact action. The distilled water may be warmed for this purpose but should not be boiled. After prolonged use, the solution should be filtered to remove suspended matter introduced into tank 20 by surface impurities on the metal blank plates I. No initial cleaning of the blank plates I, I etc., is required as a thorough detergent action of the aforesaid electrolyte and the aforesaid electrical treatment, cleans impuritiesv from the surface of raw plate blanks I, I, etc.. Exhaustion of the treating electrolyte is shown by failure of the aforesaid characteristic blue line to appear on plates in process and can be remedied by renewal of the electrolyte chemicals or solution as required.

(XI) Ageing of condensers before use Ageing of the completed condenser elements.

52 shown in Fig. 16 is accomplished as shown in Fig. 24, and requires a period of about 5 minutes per condenser. A suitably driven generator Ill-regulated by rheostat 89 to deliver about 500 volts D. C. feeds bus bars 90 and M to which a plurality of resistances 92, 92 etc. of about 10,000 ohms each are connected. Clips 93 are provided so that a condenser roll 52 can be placed in circuit with bus bars 90, 9| in series with resistance element 92. Current of correct polarity is then applied by closing switch 94 for a period of about 5 minutes and not longer than 12 minutes. This causes the gum content, of the mixture 24 used as aforesaid, to be driven into operative condition with respect to the electrodes of condenser element 52.

(XII) Testing condensers To test completed condenser elements 52, a circuit such as shown in Fig. 25, may be used. Clips I 04 place condenser 52 in circuit under control of switch 96. When switch 96 contacts with contactor 91, with switch I04 closed to protect milli-ammeter I02, direct current source MI is applied to condenser 52 at correct polarity through choke coil 99. After a brief time interval, switch I03 may be opened temporarily to obtain the milli-ampere reading of leakage current on meter I02. This leakage current will be negligibly small. Switch I03 is then closed and switch 96 is moved to contact with contactor 98, whereupon the alternating current source I00 is applied to condenser 52 and readings of voltage and current are observed. These readings may be co-related to the capacity of the condenser 52 in the usual manner. By the impedance method, the capacity in micro-farads is given by the equation,

As an example, a condenser unit 52 made with.

a single treated positive electrode plate I as aforesaid, may have an area of 4 square inches and be treated according to Fig. 23 with the parallel operated voltage of generator ll, Fig. 23, adjusted to some value, such as 475 volts which will characterize plate I with the equivalent of l mfd. of capacity in a finished condenser assembly 52. If test on a circuit, as shown in Fig. 25, shows too small a capacity reading, the treating voltage used in Fig. 23 may be slightly reduced during the parallel connection operation as aforesaid. Very uniform production of condensers, such as 52, can be attained in this 'manner.

(XIII) Circuit arrangements Circuit arrangements for condensers or blocks employing one or more units, such as 52, are shown in Figs. 26, 27, 28, 29, and 30.

In Fig. 26, the common negative electrode 45 of a roll condenser, such as 52 hereinbefore described-has cooperating condenser elements I05 and I06 prepared as hereinbefore described, and

one series section (I01, I08, I09) as aforesaid in a filter arrangement H0 provided with cooperating choke coils II2 and H3 as well as output terminals III. The conventional equivalent circuit corresponding to Fig. 26 is shown for comparison in Fig. 27. The series condenser assembly, I01, I08, I09 is necessary only at the input of filter circuit H0 at which point the alternating current component usually supplied to terminals H0 is large.

In Fig. 28, two series connected condenser assemblies 52, and 52 are shown. Unit 52 has a prepared positive plate I in operative relation with anegative electrode 65, while unit 52 has a prepared plate I as aforesaid in operative relation with a negative electrode 65 In Fig. 29, three series connected units 52, 52 and 52 are used, in which unit 52 has elements I 45,, unit 52 has elements I and unit 52 has elements I, 65 as aforesaid.

In Fig. 30 parallel connections for three units 52, 52 52 are shown, in which unit 52 has elements l, 35 unit 52 has elements 415 and 1, and unit 52 has elements I and 45 as aforesaid.

Having now fully set forth my invention and the mode of making and using same in a complete exemplification;

I claim:

1. In the electrical condenser art, a condenser composed of a common negative electrode and a plurality of separated filmed electrodes and impregnated fibrous sheets separating said negative electrode from said filmed electrodes, characterized by the fact that said negative electrode overlaps each of said filmed electrodes.

2. In the electrical condenser art, an-operating electrolyte for an electrolytically prepared condenser consisting of a mixture of approximately ten pounds of gum arabic, and forty pounds of v glycerine.

3. An electrolytic condenser comprising a roll having convolute layers of anode foil and cathode foil, a dielectric film upon the anode foil in contact therewith, the foil at the exterior of the roll having an outer turn completely encircling the roll, the outer end of said outerfoil-protruding beyond the end of the other foil, and directly overlying and engaging the underlying area of said outer foil.

4. An electric condenser comprising a roll having convolute layers of anode foil and cathode foil,

a dielectric film upon the anode foil in contact therewith, the cathode foil being at the exterior of the roll and having an outer turn completely encircling the roll the outer end of said cathode foil protruding beyond the end of the anode and directly overlying and engaging the underlying cathode area.

5. An electrolytic condenser comprising an active capacity producing unit, including electrode foils with intervening porous means interleaved therebetween and in contact therewith and having film-forming electrolyte retained therein, a wrapper completely enclosing said active unit, said active unit having terminal leads protruding from said wrapper, a casing enclosing said wrapped unit, and means rigidly'retaining said unit in fixed position within said casing.

6. An electrolytic condenser comprising an active capacity producing unit, including electrode foils, interleaved porous means in contact at its opposite faces with the respective foils and having film-forming electrolyte retained therein, a leaktight wrapper completely enclosing said unit, terminal leads protruding through said wrapper, a casing enclosing said enwrapped unit, and a watertight filler occupying the gaps between the walls of said casing and said enwrapped unit. 7. An electrolytic condenser comprising an active capacity producing unit including enrolled metal foil electrodes with intervening absorbent material having electrolyte retained therein, an

insulating wrapper about said roll, tabs integral with the respective electrode foils, terminals electrically and mechanically bonded to said tabs, pitch completely embedding the bond between said tabs and said terminals, and an outer casing enclosing said entire unit with the terminals accessible through said casing.

8. A plurality of electrolytic condensers of the roll type arranged in a single unit comprising a common coiled cathode, a plurality of coacting filmed anodes coiled with said common cathode to co-operate therewith and spaced from each other, an absorbent separator arranged between said common cathode and said anodes, and an electrolyte carried by said absorbent separator.

9. The process of making an electrolytic condenser comprising winding two metal electrodes at least one of which is filmed with thin interleaving porous spacers, impregnating said spacers with a homogeneous glycerine gum syrup electrolyte which has been subjected to a temperature of at least C. for at least thirty minutes, enclosing the condenser body thus formed in a moisture-proof container, and sealing the same against the entrance of moisture.

10. The process of making an electrolytic condenser having va plurality of metal electrodes at least one of which is filmed, and interleaved porous spacers, which comprises heating a liquid electrolyte containing gum arabic and polyhydroxy alcohol for at least thirty minutes at atemperae ture of 140 C. to C. to reduce the electrolyte to a semi-gumming mass devoid of moisture, impregnating the spacers with the hot electrolyte and allowing the spacers to cool, then winding the electrodes with the impregnated spacers interleaved therewith and sealing the condenser in a moisture-proof container.

11. An electrolytic condenser comprising two metal electrodes at least one of which is filmed, thin porous spacers wound therewith, a stable electrolyte containing gum arabic and polyhydroxy alcohol devoid of moisture and held in and on said spacers and in contact with said electrodes, and means for enclosing and sealing the same to exclude moisture.

12. An electrolytic condenser comprising a plurality of metal electrodes separated by interleaving absorbent material impregnated with a homogeneous syrup electrolyte devoid of moisture and consisting of-a cooked mixture of gum arabic and glycerine. i

13. The process of making an'electrolytic condenser having a plurality of metal electrodes one of which at least is fihned, and interleaved spacers, comprising impregnating the spacers with a glycerine from which all moisture has been excluded held in and on said spacers and in contact with said electrodes, and means including a moistureproof fibrous wrapper for enclosing and sealing the same to exclude moisture. 

